The Internet Protocol Multimedia Subsystem (“IMS”) is an architectural framework for delivering Internet Protocol (“IP”) multimedia to mobile users, such as users of smart phones or tablet computers. An IMS core network (“IMS core”) permits wireless and wireline devices to access multimedia, messaging, and voice applications and services. IMS standards and specifications have been promulgated by the 3rd Generation Partnership Project (“3GPP” ™). To allow the IMS core to be integrated with Internet resources, the 3GPP specifications use Internet Engineering Task Force protocols within the IMS core, such as Session Initiation Protocol (“SIP”) and Diameter. SIP is a signaling protocol used for creating, modifying and terminating two-party or multiparty sessions consisting of one or several media streams. A mobile device registers its IP address with a SIP registrar server within an IMS core by generating and sending a SIP request message with a “REGISTER” method token. Once registered, a mobile device may subsequently establish multimedia sessions via the IMS core.
An IMS client (or IMS stack) software component on a mobile device allows one or more applications on the mobile device to register for various application services that are available on the IMS network, such as Voice over LTE (VoLTE), Rich Communication Services (RCS), Short Message Service over Internet Protocol (SMS over IP), and Presence. If the registration is successful, the mobile device application may then take advantage of the functionality offered by the application service to which it is registered. If the registration is unsuccessful, however, then the application will be unable to take advantage of the offered functionality.
Increasingly, mobile device users take advantage of multiple mobile devices to access services offered by an IMS network. For example, a single user may own a smartphone, a tablet computer, and a wearable device such as a watch that are all capable of using IMS services such as voice and video calls. In such instances, the user may wish to have the option of choosing which device to use in a given circumstance based on a variety of environmental factors and personal preferences. For example, a user may prefer to receive a video call on a tablet rather than on a smartphone, the user may prefer to receive voice calls only between certain hours, or the user may prefer to avoid receiving any IMS services on a device with a low battery level. Despite many such user preferences, however, traditional IMS networks typically forward an incoming call to a single default device rather than alerting multiple devices in order to give the user a choice of which device to use. As a result, mobile device users often experiences frustration by having no choice other than to take a call on a device that may not be optimal or convenient under the user's present circumstances. These and other problems exist within the current IMS architecture. Thus, the need exists for a system that overcomes the above problems, as well as one that provides additional benefits. Overall, the examples herein of some prior or related systems and any associated limitations are intended to be illustrative and not exclusive. Other limitations of existing or prior systems will become apparent to those of skill in the art upon reading the following Detailed Description.